Smaller players are now entering into the enterprise UC market in addition to consumer tools. Note that this is a direct competition to Skype. One such new incumbent is Goober ( http://www.goober.com). Not only are they offering the usual phone/video/long distance offloading services but they are also providing HD services through its multi-way conferencing solutions.
And oh, by the way, they provide an iPhone app as well. I will try to post some revenue numbers in the next few months on how they perform.